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UNITED STATES PATENT OFFICE.

CARL D. EKMAN, OF 57% OLD BROAD STREET, LONDON, ENGLAND.

METHOD OF TREATING WOOD IN ORDER TO OBTAIN FIBER SUITABLE FORPAPER-MAKING, 84c.

SPECIFICATION forming part of Letters Patent No. 253,357, dated February'7, 1882.

Application filed December 10, 1881.

To all whom it may concern.-

Be it known that I, CARL DANIEL EKMAN, of Old Broad Street, in the cityof London, England, have invented a new and Improved Method of TreatingWood in Order to Obtain Fiber Suitable for Paper Making, 860., (forwhich I have obtained Letters Patent of Great Britain No. 3,062, datedJuly 13, 1881, a brevet of France, dated November 10, 1881, and a brevetof Belgium, dated November 12, 1881,) of which the following is adescription.

My invention has for its object the production from wood of a fiber orfibers suitable for paper-making and for other purposes; and myinvention consists in boiling wood under pressure with a solutioncontaining sulphurons acid and magnesia, in the proportions and underthe conditions hereinafter stated. Potash and soda may also be employedfor the purpose; but I prefer to use magnesia, as being more economicaland having chemical properties which render it peculiarly suitable, andtherefore the invention will be described'with especial reference to theuse of magnesia.

It will be convenient to describe the process as applied to Swedishwhite fir of good quality and fine grain,'pre\-*iously freed from barkand knots and out into pieces of suitable form and size-say of half tothree-quarters of an inch long-and subsequently crushed between rollers,sum to render the wood easily permeable by the liquid solution, in orderto produce fiber of the best quality for paper-making; but the mode ofpreparation may be varied. White fir and trees of the same order areespecially suitable, as they give long and strong fiber, very clean, andsimilar in its properties for paper-making to that of flax, and thiskind of wood is comparatively cheap and abundantin many countries. Thesuitableness of other kinds of wood for the purpose depends much uponthe length and properties of its fiber, as well as on the facility ordifficulty found in dis-r solving the incrusting matter, so that in the4 5 selection of wood much will depend on the pur-' pose for which thepulp is required; but in, general that wood which is very resinous isavoided because of the difficulty found in dis solving the incrustingmatter sufficiently to ob- 5o tain good cellulose.

The raw material of wood.

(No specimens.) Patented in England July 13, 1881, in France November10, 1881, and in Belgium November 12, 1881.

is selected with more or less care, according to the purpose for whichit is required; but when.v a superior quality of pulp has to be producedall exceptionally resinous and hard pieces of wood, as well as thosedamaged by rot, are to be thrown out. Wood in small pieces, thusprepared, (and if necessary duly sorted,) is put into a jacketed boilerlined with lead or a suitable compound thereof, and mounted on trunnionsfor the convenience of filling and empty- 6o ing. The boiler may bevertical and cylindrical, of about four feet diameter inside and twelvefeet between the two ends. The wood, is put into the boiler until it iswithin about two feet and the solution to within about four inches ofthe top end of the boiler; but the quantity-of wood is limitedonly bythe condition that it should be completely covered with the solutionduring the whole boiling process.

In the preparation of the boiling liquid or solution the proportionsbetween the sulphurous acid and the magnesia found to be mostadvantageous are about two equivalents of the phurous acid. The boileris filled with this solution to such an extent that while the wood isperfectly covered by it there is yet sufficient room left in the upperpart to form a steamspace. The wood is prevented from rising above theliquid during the boiling by the pressure thereon of a perforated leadenplate. After the boiler has been charged with wood and the solutionunder the conditions stated a cover is bolted on and made tight byordinary means. Steam of from ten to fifteen pounds pressure on thesquare inch is now passed gradually into the jacket of the boiler, thecondensed water returning into the generating-boiler in the usual way.When the pressure in the boiler itself (not the jacket) begins 5 toexceed five pounds to the squareinch a valve placed at the highest partof the boiler for the purpose is opened, so that a small quantity of gasand steam escapes. The pressure of steam in the jacket is graduallyincreased as the steam-pressure is seen to rise in the boiler itself,and it is preferred that the pressure in the jacket should not exceedthat in the boiler by more than thirty pounds per square inch. As thepressure in the boiler increases more gas and steam are allowed toescape from the before-named valve, the object being to prevent theburning or discoloration of the wood during the operation.

For boilers of the size above referred to, the boiling is or may beconducted so that after two hours the pressure in the inner boiler isten pounds, and this is increased twenty pounds per hour for the twohours, in the next hour fifteen pounds, and in each of the two followinghours ten pounds. When the pressure hasreached eighty-five or ninetypounds per square inch, or thereabout, the boiler is allowed to remainat that pressure for from one to three hours, the completion of theoperation being indicated by the smell. In case of any burning ordiscoloration taking place, (which is easily detected by the odoremitted or by the color of the liquid,) steam is blown off, the massturned out of the boiler, and waterthrown on it; but if there be no signof burning the mass may remain in the boiler for some time after steamhas been blown oft. The cover is then taken off, the boiler turned onits trunnions, and the fiber strained off from the liquor. The fiber iswashed and beaten in the usual manner; and the liquor may be treated inany suitable way in order to obtain a gummy matter, which for somepurposes may be used as a substitute for ordinary dextrine; also toobtain other useful products, or for the recovery of the chemicals.

If it be desired to obtain a fiber less approachin g pure cellulose, bydissolving asmaller part of theincrusting matter of the wood a weakersolution and lower pressure may be used. The solution employed may alsobe varied to aconsiderable extent, it being understood, as a generalrule, that if the salt be more basic than that above described theincrusting matter will be less completely dissolved, and if more acid(and waste is to be avoided) there is more liability to burning. Thepressure above indicated may in some cases be varied.

The completion of the boiling operation has in the foregoing descriptionbeen fixed at about eighty-five to ninety pounds pressure, because goodresults may be relied upon within this limit; and for practical purposesincrease of pressure beyond this point may be attended withdisadvantage, economically; but I do not confine myself to this limit,because good results have been obtained at a pressure up to one hundredand ten pounds, and even above this.

The fiber resulting from the above treatment of the wood is suitable forgood ordinary printing-paper, and may be made suitable for superiorpapers by means of treatment with bleaching-powder and the resultingsolution of an amber color contains a large quantity of gummy matterresembling ordinary dextrinc and other incrusting and soluble matterswhichfthe wood contained, and which may be made more or less availablefor commercial purposes. The resulting fiber may be suitable for coarserkinds of paper, mill-boards, papiermach, and similar materials, even ifthe separation of the cellulose from the incrusting and other matter hasnot been so complete as above described.

The invention can be easily applied to other kinds of wood besides thewhite fir described by modifying the process according to the productrequired and the wood used, the quality of the fiber obtained dependingupon the suita-bleness of the wood and the other abovenamed conditions.If the wood is very resinous, (although its original fiber may be good,)the resulting material may only be useful for the coarser kinds of paperand similar materials, owing to the difficulty of removing theincrusting matter.

The peculiar character of the invention will be better understood byconsidering the advantages possessed by it over the usual method, inwhich caustic soda is employed. Instead of using caustic soda, chemicalsare employed which have a far less damaging effect on the fibers, andwhich, especially when magnesia is used, are much cheaper.

In boiling with caustic soda the separation of the fiber fromtheincrustin g matter depends, as is well known, on such matter beingrendered soluble by oxidation; but it is impossible to prevent thefibers themselves from being also oxidized to some extent, therebyweakening and partially destroying them and diminishing the quantity ofpulp yielded by the wood. On the other hand, in the preparation of pulpaccording to my invention no oxidation of the fiber can occur when theoperation is properly conducted and the incrusting matter obtained is inthe form of a gummy matter of commercial value, instead of beingconverted, as by the old method, into worthless products of the humustype. Another advantage is, that the boiling can be done at about halfthe pressure required by the usual method, which is of great importancein practice. Besides that, the fiber is less liable to be weakened inthe process. A third advantage is that by this method fiber can beprepared which, without any further chemical treatment, is sufficient] ywhite to be used for ordinary kinds of paper, and is capable ofsupplying a strong good paper without admixture of other fiber. After asubsequent treatment with bleaching-powder it is made suitable for themanufacture of all the finer kinds of paper. This fiber much resembleslinen in its physical and chemical properties for papermaking, and istherefore a very valuable ma terial for this purpose. A fourth advantageis. that the solution which remains after boiling contains a gum-likesubstance, which at a small cost can be made to serve as a substi- IIO IV r 253,357 3 tube for dextriue for many purposes,.and there. Iclaimbyproduce economyinthemanufactuiie', Some- The boiling of woodunder pressure with a portion also of the chemicals used in thesolusolution containing sulphurous acid and magtion may be recovered; Afurtheradvantage nesia, in the proportions and under the condi- 15 5consists in avoiding the injurious effect on vegetions substantially asdescribed.

tation and on animal life produced, as is well known, byspent-soda lyeresulting from the G. D. EKMAN.

ordinary method or process; and, last1y,'ce1lu lose of good quality-canbe prepared at a com- Witnesses: 1 o paratively low cost by the processhereinbefore 4 WILLIAM SBENOE,

' I ALFRED H. J ONES.

described.

